Normal AC clutch function?

[Matthew Jeschke]

I've went through and rebuilt my AC system w/ new compressor & clutch, evap coil, etc etc. etc. It works like a champ. So far as I know (but didn't write down) AC pressures are in line, EVAP split & Condenser temp splits are good too.

However, I've never really had anybody answer this question to my satisfaction before. The front system is an orifice tube metering device. This has a static flow / fixed flow adjustment due to it's design. Unlike the rear system which is a TXV w/ bulb sensor which can adjust nozzle aperture via feedback from bulb sensor (super heating process).

I presume w/ an orifice tube design the AC clutch must be cycled to regulate line pressure. Otherwise high side might stack up molecules / build too much pressure due to the expansion valve being fixed (non variable nozzle) on the tube?

This question came to me when I worked on my friends' / non GM vehicles where the system doesn't utilize a orifice tube but rather a expansion valve with feedback / adjustable nozzle. Their clutches always stay on...

Or does my truck have an issue w/ AC as it cycles the AC clutch every so often while head unit has AC selected ON (I'm not turning AC on and off myself).

UPDATE: I may have answered my own question. I had been searching internet prior to posting this... Then tried one more time and came across this webpage HERE which confirms orifice tub flow is regulated via turning compressor on and off as I observed.

 

[Donal]

Yep, having the correct charge of R and air flow across the evaperator help keep pressures in operating range.

 

[Matthew Jeschke]

As in, that correct pressure is regulated by cycling the AC clutch?

 

[Donal]

 

[Matthew Jeschke]

Yes, thank you for the table... but my question isn't about line pressures. I'm asking about clutch / compressor function. Does it cycle on and off to maintain line pressure? I assume cycling of the clutch, after AC is commanded on, is typically operation.

I think I may have answered my own question... Finally found a webpage that explained fixed nozzle size w/ orifice tube requires compressor to cycle on and off.